Not to be rude, but I dont really see the difference between a 99 Z34 and a 00 SS. Same engine, same trans, generally the same chassis, near identical performance, etc. Just one came badged as a SS and the other as a Z34.

I wouldn't get too hung up on having a 'real' SS, especially in that time frame. GM was badging everything as a SS in the early to mid 00s.

 

According to some of the shows on the Velocity now Motor Trend. The SS has not been exclusive to Chevrolet. However I think Chevrolet introduced the SS or Super Sport with the 1961 Chevy Impala. It featured the 409 Motor. I have had a few Super Sports and each one had a performance package that differed from the regular Car whether it be the Impala or the Chevelle or Camaro or Nova. the Trucks weren't badged with the SS nor were the SUV's.
I had a 1963 Impala SS and a 64 back then the stance was different springs were beefier, then I had a 69 Chevelle SS in Daytona Yellow. That thing was a screamer. 90% driver if I recall. Lol
But when GM started putting the SS badge on a 4 door that broke the tradition. However I have driven the Chevy SS by Holden and it is a nice ride. To expensive though.
The Z 34 was a badge they put on the Chevy Lumina after they discontinued the Monte Carlo in 1988 or 87.
A polaroid of my old Chevelle that I wish I still had.

The Daytona Yellow Chevelle SS 396

 

Yeah, GM was slapping the hell out of that SS badge in the 2000s - Impala, Monte Carlo, Malibu, Cobalt, TrailBlazer, Silverado, HHR, SSR (not the trim but it's in the name), 2003 SS (concept).

 

I recall back in 2011 I was working here in my own home state and this secretary lady I worked with liked the Impala that I drove. It got great gas mileage I showed her the actual mileage based on the receipts and it was doing 35mpg. So she needed a new ride this old Van she drove the AC bit the dust. So she found an Impala. She called and told me she bought one a 2009 or 10 SS. It was Red and she was a Graduate of UNL (GBR). She said it gets horrible mileage. I think was Chevy did to it was give it that off the line performance and not highway. I finally got a ride in it and it was okay but not what I would have bought. I believe the suspension was a bit different and the interior was all leather. She was a farm girl and I think this thing by now will need to be replaced. Some of those cars should have been equipped with a deeper overdrive. Something to help the highway performance. Now a friend of mine has a 2016 Impala, that thing has all the toys on it. The engine will practically shut off when you stop at a Red Light.
But I would enjoy having one like it.

 

That is a bit strange that she would buy the SS if she was concerned at all about gas mileage. Big v8, 4 speed auto, and a full size car seems like an obvious recipe for bad mileage.

I'm not really sure there was much they could do about OD either. Being a 4 speed where 3rd is at or near 1:1, you can only have so big of a step there.

 

The thing was Red and she bought it on that Color only and that I had an Impala for a rental car.
A year later I finally got a ride in it. I could feel this vibration in the thing and a slight noise. I mentioned that to her. She told me I was hearing things.
Then a month or so after that she had a wheel fall off while she was braking at the end of her country lane.
She thought it was her X that loosened the lugs on it. She took the thing in to get the tires balanced and rotated, and found out the tires had worn unevenly. They told her the alignment was off.
She asked me about an all wheel alignment. I said you should do that after every new tire purchase of all 4. The tires supposedly had less than 10K and were junk.
She would never take my advise as if I was telling her something strange? Didn't matter all the driving experience I had. She knew it all. She was my age OLD
I remember her Mother telling me that she was stubborn as a mule.